1. Field of the Invention
The present invention relates in general to door closures and more particularly to electric door closures incorporated with a door lock device, which enforcedly close a door with the aid of electric power. More specifically, the present invention is concerned with electric door closures of a type which enforcedly moves a door to a so-called full-latch position with the aid of electric power when the door moves from an open position to a so-called half-latch position.
2. Description of the Prior Art
In order to clarify the task of the present invention, a known electric door closure shown in Japanese Patent Second Provisional Publication 2-4754 will be outlined in the following.
The electric door closure of the publication is incorporated with a back door lock device. The back door lock device generally comprises a lock proper mounted on a pivotal back door and a striker mounted on a rear portion of a vehicle body. Upon closing of the back door, the lock proper catches the striker to hold the door in a closed and latched position. The electric door closure includes a rotating plate fixed to a latch plate shaft of the lock proper, a lever pivotally connected to the rotating plate, a position sensor for sensing the position of the latch plate and an electric motor for actuating the latch plate through the lever and the rotating plate. That is, when the position sensor senses that the latch plate has turned from an open position wherein the latch plate releases the striker to a half-latch position wherein the latch plate incompletely engages with the striker, the electric motor becomes energized to force, through the lever and the rotating plate, the latch plate to pivot from the half-latch position to a full-latch position wherein the latch plate fully engages with the striker. Due to this movement, the back door is shifted to its fully closed and latched position relative to the vehicle body.
In the electric door closure of the publication, a measure is employed for permitting a free movement of the latch plate and the rotating plate when the electric door closure is under OFF condition. That is, in the measure, for preventing the lever from interrupting the movement of the latch plate and the rotating plate in such OFF condition, there is provided between the lever and the rotating plate a play of an amount corresponding to a rotation angle of the latch plate between the open position and the half-latch position.
However, due to provision of this play, upon operation of the electric door closure, the lever is subjected to an inoperative condition for a certain period from the time when the motor is energized to the time when the lever actually drives the latch plate. Thus, the electric door closure fails to achieve a quick door closing action.